1. Field of the Invention
The present invention relates to methods of processing pet food products made from animal hide.
2. Background Art
Pet chewing bones made from animal hide are a type of pet food product, called dog chews in the industry. There is enormous market demand for these products in advanced countries such as Japan, the United States, the United Kingdom, and Australia. Annual sales volumes may reach billions of US dollars. These products are primarily produced in Brazil, Thailand, and China and are exported to countries where there is demand. The dog chew manufacturers in China are primarily located around Shuitou Town, Pingyang County, Wenzhou. The reason for this is that Shuitou Town has the largest pig and cattle tannery centers in China and thus provides a sure supply of raw materials for dog chew production.
In the process of making dog chews, raw hide undergoes defatting and depilation treatment. It is then split into first, second, third, and fourth layers of rawhide material, which then undergo further defatting, rinsing, and sun-drying to become finished hide products. The finished hide product is then cut, soaked, plaited and shaped, dried, dyed, and flavored, and the result is animal hide dog chews. If the finished-product hide is shredded, mixed with adhesive, mould-pressed and formed, dried, dyed, and flavored, the result is an adhesive product dog chew. That is, dog chews can be classed either as animal hide dog chews or as adhesive product dog chews, depending on the processing steps. In addition, dog chews can also be classed according to the raw material as either cowhide dog chews or porkhide dog chews.
The fact that cowhide has small pores and less grease means that cowhide dog chews boast smooth and lustrous surfaces that can easily be dyed different colors and soaked to take on many delicious flavors. The aforementioned process of dyeing and flavoring consists of directly using food dyes and flavor essences on the surface of the finished product. This method is very well suited to cowhide dog chews. Because pork hides have large pores and high fat content, porkhide dog chews appear rough, plain, dull, and white. They smell of rawhide and uncooked oil. Moreover, there is no way to dye or flavor them, for their oily surface can hardly absorb any dyes or flavor essences. Therefore, although the raw material for porkhide dog chews enjoys a huge advantage in terms of availability and ease of purchase (relative to cowhide), it is difficult to change the unappealing color and odor of porkhide dog chews using the current, general dyeing and flavoring methods. As a result, cowhide dog chews have won most of the dog chew market, and porkhide dog chews have just a minor share of the market.
A goal of the present invention is to provide a porkhide dog chew processing method that can thoroughly change the original color and odor of porkhide dog chews.